Revealing Short-Term Precursors of the Strong M &gt; 7 Earthquakes in Southern California From the Simulated Stress–Strain State Patterns Exploiting Geomechanical Model and Seismic Catalog Data

Valery G. Bondur,Dmitry A. Alekseev,Igor A. Garagash,Mikhail B. Gokhberg

doi:10.3389/feart.2020.571700

Abstract

Since 2009, the stress-strain state of the earth’s crust in Southern California region is being monitored through geomechanical modelling taking into account the ongoing seismicity with magnitudes M >1. Every new earthquake is assumed to cause a new defect in the Earth's crust, leading to redistribution in the stress-strain state. With half-monthly stress-strain state updates, we found that both strong earthquakes with M ~ 7 that occurred in the area in 2010 and 2019, had been preceded by the anomalies in the strength parameter 𝐷 (indicating how close the rock is to its ultimate strength), which had emerged a few weeks to months before the main shock at a distance of 10–30 km from the future epicenter. Over the course of monitoring (nearly the decade), this approach has neither produced false alarms, nor missed events with M>7 falling within the modeling area.

Highlights

The development of seismic hazard monitoring and prediction methods is crucial for preventing and mitigating the fatalities and damage caused by strong earthquakes
With half-monthly strain state (SS) updates, we found that the two strong earthquakes with M ∼ 7 that occurred in the area in 2010 and 2019 had been preceded by anomalies in the strength parameter D, which had emerged a few weeks to months before the main shock at a distance of 10–30 km from the future epicenter
The results presented in this study have been obtained with a geomechanical modeling-based monitoring technique (Bondur et al, 2010; Bondur et al, 2016; Bondur et al, 2017; Bondur et al, 2020), allowing one to image and trace the SS evolution over the Southern California region during the period from 2009 to 2019, with the identification of SS precursor patterns preceding strong (M > 7) seismic events

Summary

Introduction

The development of seismic hazard monitoring and prediction methods is crucial for preventing and mitigating the fatalities and damage caused by strong earthquakes. The primary focus of research in this field is linked to identification of precursors, preceding high-energy seismic events (Mogi, 1985; Sobolev and Ponomarev, 2003; Viti et al, 2003; Molchan and Keilis-Borok, 2008; Paresan et al, 2015; Bondur et al, 2018; Rundle et al, 2018 and references therein). Some precursors may be recognized from the anomalous behavior of various geophysical fields, including ones rendered by the dynamics of lineament systems (Bondur and Zverev, 2005; Paresan et al, 2015), variations of the ionosphere parameters (Liu et al, 2004; Bondur and Smirnov, 2005; Bondur et al, 2007; Singh et al, 2009), and other phenomena exhibiting increased activity before earthquakes. An extreme complexity of the coupled processes and interaction mechanisms relating the subsurface mechanics during the stress accumulation (earthquake preparation) stage to potentially observable (geophysical) precursors makes the forecast a highly challenging goal, with relatively few examples of successful prediction.

Methods

Results

Conclusion